Split type multistage rolling mill

ABSTRACT

A multistage rolling mill having a roll arrangement of the Sendzimir type with each of the upper and lower half roll grouping having two drive rolls employs a separate upper inner housing carrying the upper roll half and a separate lower inner housing carrying the lower roll half, with each of the inner housings being encompassed and mounted within a separate integral and rigid outer housing. A pass line adjusting means is provided between the outer housing and the upper inner housing, and a rolling reduction adjusting means is provided between the outer housing and the lower inner housing. Various leak proof valves are used to isolate the hydraulic fluid within the automatic adjusting system to maintain the mill spring constant high, and further for roll change a separate synchronizing fluid circuit is opened up to permit the lower inner housing to drop for roll change without distrubing the initial set-up of parallelism between the upper and lower housings. The back-up rolls may be eccentrically adjustable, and the intermediate rolls may be tapered for edge adjustment.

Unite 10 States Patent Kajiwara et al.

SPLIT TYPE MULTISTAGE ROLLING MILL- Inventors: Toshiyuki Kajiwara; Kakichi Fukui;

Katsuji Mita, all of Hitachi; Akira Yamauchi, Takahagi, all of Japan Assignee: Hitachi, Ltd., Tokyo, Japan Filed: Jan. 26, 1973 Appl. No.: 326,858

Foreign Application Priority Data Jan. 28, 1972 Japan 47-010767 US. Cl. 72/242, 72/243 Int. Cl B2lb 13/14, B2lb 29/00 Field of Search 72/242, 243, 241, 237,

References Cited UNITED STATES PATENTS Jan. 7, 1975 [57] ABSTRACT A multistage rolling mill having a roll arrangement of the Sendzimir type with each of the upper and lower half roll grouping having two drive rolls employs a separate upper inner housing carrying the upper roll half and a separate lower inner housing carrying the lower roll half, with each of the inner housings being encompassed and mounted within a separate integral and rigid outer housing. A pass line adjusting means is provided between the outer housing and the upper inner housing, and a rolling reduction adjusting means is provided between the outer housing and the lower inner housing. Various leak proot" valves are used to isolate the hydraulic fluid within the automatic adjusting system to maintain the mill spring constant high, and further for roll change a separate synchronizing fluid circuit is opened up topermit the lower inner housing to drop for roll change without distrubing the initial set-up of parallelism between the upper and lower housings. The back-up rolls may be eccentrically adjustable, and the intermediate rolls may be tapered for edge adjustment.

10 Claims, 12 Drawing; Figures Patented Jan. 7, 1975 6 Sheets-Sheet 1 FIG. 2

Patented Jan. 7, 1975 I 3,858,424

6 Sheets-Sheet 25 Patented Jan. 7, 1975 6 Sheets-Sheet 5 Patented Jan. 7, 1975 3,858,424

6 Sheets*Sheet 4 Patented Jan. 7, 1975 3,858,424

6 Sheets-Sheet 6 I SPLIT TYPE MULTISTAGE ROLLING MILL BACKGROUND OF THE INVENTION The present invention relates to a split type multistage rolling mill, and more particularly to a split type multistage rolling mill having a special arrangement and construction with an outer housing and an inner housing combined.

Multistage rolling mills that have been widely put into practical use or known in the industry at present are: of the Sendzimir mill type of the Sendzimir Cornpany; of the Rohn mill type of the Sundbich Company; and of the Cluster mill type of the Textron Company. These mill types serve for both 2-high and 4-high mills.

The Sendzimir mill accommodates rolls within an integral housing, and conducts the rolling reduction adjustment of the work rolls by means of eccentrically 1 mounted back-up bearings, wherein rotation of the eccentric mountings will move the back-up bearings toward and away from the roll gap for correspondingly changing the gap. The merits of this type of mill are that the work rolls have very little deflection, and that the mill spring constant is quite large. However, there are also disadvantages of this type of mill as will be set forth. Because of the integral housing, the distance between the work rolls or the roll clearance is small due to the geometrical dimensional relationships, so that the range of use of the work roll diameters is limited to a small one. Further, the roll clearance cannot be made large, so that a plate passing operation is difficult, and quite frequently there is a roll failure with the accidental cutting of the rolled material, and the removal of cobbles is difficult. Because ofthe rolling reduction adjustment by the eccentricity of the. back-up bearings, mobility is deficient, the rolling pressure cannot be precisely measured, and the rolling reduction of the work rolls cannot be linearlymeasured.

The Rohn mill is so constructed that a housing for accommodating groups of rolls is split into upper and lower parts. The split housings are supported by four stanchions or two stanchions and hinges. The rolling reduction adjustment of the rolls is carried out in such a way that the upper split housing is pressed down by rotatable screws of the respective stanchions, by means of an electric motor disposed on the upper split housing. The merit of this mill is that since the housing is split, the disadvantages noted above with respect to the Sendzimir mill are not involved. On the other hand, there are disadvantages as set forth below. Since the housing is split, the mill spring constant is considerably lower than that of the integral type housing mill of the Sendzimir type and accordingly the plate thickness accuracy deteriorates. Because of the electricallyoperated rolling reduction,'the rolling reduction responsiveness is poor, and the tuning performance of the rolling reduction control is inferior, so that a precise automatic plate thickness control is impossible. Also, it is difficult to mount a pass line adjusting mechanism.

On the other hand, the Cluster mill type, which may serve for both Z-high and 4-high mills, is excellent in usage with a multistage rolling mill. However, since it is a joint used mill, the spindle or number of spindles for driving the rolls is limited to one for each of the upper and lower parts. This leads to the disadvantage that a peculiar roll arrangement must be adopted,

which is basically different from the roll arrangement of well known multistage rolling mills such as the Sendr and accurately controlled.

zimir mill. More specifically, in the well known roll arrangement of Sendzimir mill type with 20 rolls, in case of a drive with one spindle for each of the upper and lower parts, it is inevitable to drive the second intermediate rolls. This leads to the disadvantage that such pressure by rolling pressure as brings the first intermediate rolls into contact with the second intermediate rolls becomes smallerthan one in the direction of a component force, and that in the case of the large reduction rolling with small diameter work rolls, the rolling being an advantage of the multistage rolling mill, no

torque can be transmitted from the driving rolls in re sponse to rolling torques, to make: the rolling impossi ble. In the case of a multistage rolling mill of 12 rolls, the roll driving system with one spindle for each of the upper and lower parts is impossible insofar as back-up bearings are used for reinforcement. Further, in the Cluster mill, the diameter of the driving rolls need be made large in order to keep torsional rigidity thereof; as a result however, the effect of a roll crown adjustment acts on the work rolls through the driving rolls of high flexual rigidity and hence it decreases remarkably. In the multistage rolling mill, it is known to provide the end portion of each intermediate roll of a tapered shape, to prevent edge drop of a material to be rolled. In this respect, the Cluster mill has a disadvantage in that the load is non-uniformly exerted on the back-up bearing to induce slip so that measurement cannot be adopted, since the intermediate rolls are held in contact with the back-up bearings therein.

SUMMARY OF THE INVENTlON It is an object of the present invention to provide a multistage rolling mill which has the advantages of a Sendzimir system of a rolling mill that can use work rolls of small diameter without large deflection or or deformation of the rolls, and is able to use the work rolls over the wide range of diameters. Further, the present system obtains work roll gaps of a wide range while obtaining plates with very uniform thickness by the operation of the mill under a large rolling pressure. The pass line may be adjusted easily (Further, the thickness for the width direction of a plate may be controlled in addition to the length direction of a plate with high accuracy. Further, there are meansv for supporting the thrust forces of the work. rolls, in their axial direction, at a constant position for the work rolls in spite of large variations of small roll diameter. The initial pass between the upper and lower work rolls may be easily A characteristic of the present invention is such that a construction of a multistage rolling mill with roll arrangements of the Sendzimir system in which each of an upper half roll group and a lower half roll group has two drive rolls respectively so as to be able to operate the mill under high rolling pressure, in combination with each of an upper inner housing for accommodating the upper half roll group and a lower inner housing for accommodating the lower half roll group is accommodated in the integral outer housing, which has high rigidity for a high mill spring constant. The upper half roll group and the lower half roll group each have two drive rolls respectivelyand make the mill spring constant large by compensating the mill deformation for thickness direction of a plate to be: roilled through the natural spring constant of the rolling mill and pressure of a hydraulic jack between one of a pair of the inner housing for accommodating a roll group and an integral outer housing for accommodating the pair of inner housings.

BRIEF DESCRIPTION OF THE DRAWINGS I FIG. 1, with the left hand portion being partially broken away in section;

FIG. 3 is an enlarged schematic view showing the roll arrangement in the multistage rolling mill of the present invention;

FIG. 4 is a view taken along line IV-IV in FIG. 2, with portions broken away in section;

FIG. 5 is a roll development view as taken along line VV in FIG. 1, with the adjacent drive mechanism being shown, and portions partially broken away in section;

FIG. 6 is a cross-sectional view taken along line Vl-VI in FIG. 1;

FIG. 7 is an end view of the structure shown in FIG.

FIG. 8 is a cross-sectional view taken along line VIII- VIII in FIG. 1;

FIG. 9 is an end view of the structure shown in FIG.

FIG. 10 is an enlarged plan view of one end ofa front central door that is shown in FIG. 1;

FIG. 11 is a block and schematic diagram showing an embodiment of a controlled system of a rolling reduction adjusting device according to the present invention; and

FIG. 12 is a schematic diagram showing an embodiment of the roll gap adjusting device according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION For purposes of illustration, a preferred embodiment of the present invention is shown in the various Figures of the accompanying drawing, and relates to a multistage rolling mill of the -stage roll arrangement.

As shown in FIGS. 1 and 3, each of the upper and lower roll groups consist ofa work roll 1, the first intermediate rolls 2 (two being shown), the second intermediate rolls 3 (three being shown) and the eccentric back-up bearings 4 (four being shown). The roll groups are accommodated in an inner housing which is split into upper and lower parts. The upper roll group is accommodated in the upper inner housing 5, and the lower roll group is accommodated in the lower inner housing 6. The upper and lower inner housings 5 and 6, with their respective roll groups carried thereby, are mounted for relative vertical movement with respect to each other within a stationary integral or one rigid piece outer housing 7, which in the side elevation view of FIG. 1 is in the form of a rectangle, and as shown in FIG. 2 has two such closed rectangular loop integral sections rigidly joined together by means of rigid connecting means in the axial direction of the rolls.

As shown in FIG. 1, between the outer housing 7 and the upper inner housing part5, there is provided a pass line adjusting device 8, which may be constructed as a wedge, screw, linear actuator or the like to move the upper housing part 5 relative to the outer housing part 7 in the vertical direction and maintain such pass line adjusted position. The pass line adjusting device 8 adjusts the horizontal position of the work roll with respect to other equipment, for example, a deflector roll, not shown.

On the opposite side of the pass line adjusting device 8, as shown in FIG. 1, particularly at the lower part of the rigid outer housing 7, a rolling reduction adjusting device 9 is provided which consists of a hydraulic ram and cylinder. The rolling reduction adjusting device adjusts the roll clearance or gap by moving the lower inner housing 6 in the vertical direction relative to the outer rigid housing 7, and holds such relative position. The illustrated hydraulic jack formation may be altered, for example to provide a known type of screw adjusting mechanism.

As shown in FIGS. 1 and-4, movement of both the upper and lower inner housings 5 and 6 in either axial direction of the rolls is limited or fixed by means of thrust stoppers or keeper plate guides 20, 20A. These guide plates 20, 20A are bolted to the opposite sides of the outer housing 7, as shown. Thus, axial movement of the inner housing parts is prevented while vertical movement of such parts relative to the outer housing 7 is permitted for the previously mentioned adjustment purposes.

As shown in FIGS. 1, 2 and 10, the work rolls 1 are fixed in the axial direction of the rolls by means of a front central door 50 and a similarly constructed back central door (not shown); preferably the front and backdoors are of identical construction. The front central door 50, as shown in FIG. 2, mounts a vertical axis roller 57 engages the sides of the work rolls 1 with thrust pad bearing 31 shown in FIG. 5. The front central door 50 is fixed relative to the outer housing 7 by means of a bracket 53 at one end, to be described, and a bracket 51 mounted on the outer housing 7 and provided with hinge means mounting the door 50 for swinging movement about-a vertical axis. The bracket 53 is more clearly shown in FIG. 10 wherein the adjacent end 56 of the front central door 50 rotatably carries thereon a hook 52 driven by means of a disc 55. A tapered or wedge portion of hook 52 engages with a tapered or wedge portion of the bracket 53 by rotation of the disc 55 to fix or secure the end 56 of the front central door to the outer housing 7 at the side opposite from its hinge. Since the position of the pass line is constant, although rolls of large or small diameter are used for the rolling mill, this central door construction is able to support the thrust forces of the work rolls in the axial direction of such rolls.

As shown particularly in FIG. 5, the second intermediate rolls 3 are fixed in the axial direction of the rolls by means of the thrust pad bearings 32, which are mounted on the front doors 19 shown in FIGS. 1 and 2, which doors are mounted on the inner housing parts 5 and 6, respectively, by hinges; there are further provided back doors identical to the front doors 19 at the other side of the rolls, and not shown. The drive rolls of FIGS. 5 and 3 for transmitting the rotational driving force of the rolling mill are provided by the two upper second intermediate rolls 3A and the two lower second intermediate rolls 38, with four drive rolls being thus provided for both the upper and lower roll groups. Accordingly, there are also provided four drive spindles 26 that are respectively connected to the four drive rolls through flexible couplings. Each drive spindle 26 is coupled through a universal joint to a reduction gear 11 inside of a suitable gear box 27, with the reduction gear being driven by a motor, not shown.

In FIG. 5, the upper and lower first intermediate rolls 2 are each tapered at one end, with the tapered ends of the rolls being opposite from each other; further, they are coupled to the rods 28b ofa lateral adjusting device 28 through universal joints and a pull rod 25. The rods 28b have screw means engaged with the frame 28a and drivingly carry sprockets 28c, which are in turn drivingly engaged with chains 28d, which chains are driven by a device, not shown, of the lateral adjusting device. In the specific embodiment, the right end 12 of the upper first intermediate roll is tapered, while the lower first intermediate roll is tapered at its end 13 remote or opposite from the end 12. These rolls are respectively moved in their axial direction by rotating the rods 25 by means of the chains 28d, sprockets 28c and rod 28b, so that the working initiating ends of the tapered form coincides with both end parts of material 21 to be rolled, so as to prevent edge drop of the material 21 to be rolled.

Roll re-arrangement or change is easily accomplished with the structure of FIG. 1, by lowering the lower inner housing part 6 by means of the ram 9 so that the wheels 14 carried by the lower inner housing part 6 will engage the rails 15 that are rigid with respect to the outer housing part 7; it being understood that normally there is a space in the vertical direction between the wheels 14 and rails 15 during roll operation. With this construction, the lower roll group can be removed singly, or the upper and lower roll groups can be simultaneously removed from or placed into the other housing 7 along with the corresponding inner housing part or parts by means ofa lateral roll change drive device, not shown.

In FIGS. 6 and 7, there is illustrated a roll crown adjusting device, which is provided for one or both of the upper and lower central back-up bearing pairs 4A. The device effects the crown adjustment of the rolls by eccentrically pressing down the central back-up bearings 4A in such a way that a partial gear 34 that is fixed to a central shaft is rotated according to the desired adjustment by means of a rack bar, not shown. The relatively stationary mounting 36 for the bearing of a shaft carrying the partial gear 34 is eccentric so that with rotation of the partial gear 34, the back-up bearings 4A will relatively move.

The roll crown adjusting device of FIGS. 8 and 19 is provided for one or both of the upper and lower both side back-up bearing pairs 4 B. The adjusting device of FIGS. 8 and 9 is similar to that described above with respect to FIGS. 6 and 7, and will eccentrically press down the opposed sides back-up bearings 4B by rotation of the partial gear 35 with a suitable rack bar, notshown, so that the shaft drivingly connected to the partial gear will be thereby rotated in its eccentric bearing to move relative to the mounting 37 for adjustment purposes.

The rolling reduction adjusting device or ram 9 is controlled by a control system as shown in FIG. 11, which system is generally known and therefore will not amplifier 300, a pressure cell 400, a position detector 500, and a thickness gauge 600. The output amplifier 300 operates a pencil type DC. motor 304 for low inertia rotation at constant speed through an automatic speed regulator 302 and an automatic pulse phase shifter 303 according to an electric signal from the automatic gauge control 200. A pilot generator 305 generates an electric signal proportional to the rotational speed of the DC. motor 304, which signal is fed back to a summing point 301. The rotation of the DC. motor is transmitted mechanically to a cam 105 through a rotary shaft 111 and a differential gear 106. The cam 105 drives a piston rod 104 of a pilot valve 103 upwardly and downwardly. While the pilot valve is opening, the oil from an oil reservoir or pan 101 is transmitted to a ,hydraulic cylinder 107 by means of the oil pump 102 under pressure through the conduits as shown and the pilot valve 103. When the piston of the hydraulic cylinder 107 is moved upwardly according to the above op eration, the oil on the other side of the piston in the by draulic cylinder is transmitted to the main cylinder of the rolling reduction adjusting device 9 or hydraulic jack to upwardly move the inner housing 6 through the ram of the hydraulic jack. The movement of the piston within the hydraulic cylinder 107 is detected as a rotational quantity by a rack bar on the piston rod 108 and a rotatably mounted pinion engaging with the rack bar 108, and the rotation of the pinion is fed back to the differential gear 106 through a position detecting mem' her 109. By the rotation from the position detecting member 109, the cam is restored to an initial condition. A pressure in hydraulic cylinder 107 or the main cylinder 90 is detected as an electric signal in the pressure cell 400, which electric signal is transmitted to an operating circuit and is based on the rolling pressure P as the pressure in the pressure cell 400. The natural spring constant Kn of the rolling mill which has been determined, together with the rolling pressure P, will operate a strain aP/Kn (a: constant), and an electric signal proportional to the strain is transmitted to the summing point 202. Since the rotational angle of the DC. motor 304 is proportional to a roll position in the vertical direction, the rotation derived from the rotary shaft 111 by gear means 110 or the like is proportional to the changed displacements with respect to the vertical direction, that is, the roll position, as determined by position detector 500 with a suitable screw means. An electric signal (S) proportional to the roll position is thus'transmitted by the position detector 500 to the summing point 202. This electric signal (S) and the strain signal aP/Kn is added by the operating circuit 201, so that the added signal (S aP/Kn) is compared with an electric signal (Hd), which latter electric signal corresponds to the plate thickness as produced and transmitted by a thickness gauge 600 provided on the rolling mill; accordingly, an electric signal proportional to the difference between the above signals, that is (S aP/Kn Hd) is transmitted to an electric servo motor 203 which amplifies and transmits the signal to the summing point 301. The position of the work roll 1 is thereby controlled by this signal.

Since the deflection or deformation of the rolling mill is compensated by the BISRA type automatic gauge control, the mill spring constant is substantially raised.

The high mill spring constant makes good use of the advantages of the Sendzimir system as can rolling with the work roll of the small diameter under high pressure. Further, a control system ofa hydraulic jack 9A, which is provided between the lower inner housing 6 and the outer rigid housing 7,-with pairing of the outer housing 7, comprises a hydraulic roll positioning apparatus 100A, a BlSRA type automatic gauge control 200A, an output amplifier 300A, a pressure cell 400A, a position detector 500A, and a thickness gauge 600A. The control system is detachably connected with the control system for the hydraulic jack 9 by an electrical coupling 700. Plate thickness for plate width direction is controlled by operating each'of the systems or by operating the systems in cooperation with each other with the coupling 700 coupled.

After rolls have been changed, the roll gap between the work rolls is reduced to zero so as to make the roll gap along the roll axial direction uniform and to set the scale of the roll position detector. Once zero point adjustment has been accomplished after roll change, adjustment of the roll gap is by the use of a synchronizing cylinder as shown in H6. 12. Hydraulic passages are provided in parallel with conduits or passages from the hydraulic jacks 9, 9A to the control system 801. The hydraulic passages are provided with valves 807, 807A, leakless stop valves 806, 806A, and leakless stop valves 811, 811A for liquid respectively. The hydraulic passages are joined with each other between the leakless stop valves 811 and 811A to lead to the electromagnetic valve 813. The synchronizing cylinder arrangement comprises two cylinders 802and 802A, with the same dimensions; identical pistons 804 and 804A of the cylinders 802 and 802A are connected with each other by a coupling 803. One side. of each of the cylinders 802 and 802A is communicated with each of the passages respectively between the leakless valves 806, 806A and the leakless valves 811, 811A through respective valves 805, 805A as shown in FIG. 12. An electromagnetic valve 808 is used for controlling the position, that is the opening and closing of the leakless valves 806 and 806A by the use of hydraulic operation. A further electromagnetic valve 812 is used for controlling the opening and closing of the leakless valves 811 and 811A by hydraulic operation.

In operation of the device in FIG. 12, after first assemblying the group of rolls, the valves 807, 807A, the leakless stop valves 806, 806A, 811, 811A and the electromagnetic valvesd 813 are all opened, and oil or hydraulic fluid is thereby supplied to the cylinders 90 and 90A of the hydraulic jacks 9 and 9A, respectively, so that the lower inner housing 6 is moved upwardly, so that accordingly the lower work roll 1 is brought into contact with the upper work roll 1. At the same time, the operating positions of the control system 801 and the synchronizing cylinders 802 and 802A are adjusted according to the diameter of the rolls that have just been newly supplied to the rolling mill, that is, their positions are adjusted to reflect that the roll gap is zero for calibration purposes. After this operation, the leakless stop valves 811 and 811A are closed to thereby isolate the hydraulic system shown in FIG. 12 above such leakless stop valves 811 and 811A. During rolling, the leakless stop valves 806 and 806A are closed by the electromagnetic valve 808; this will have the effect of greatly reducing the oil quantity supplied to the hydraulic jack by isolating all of the hydraulic fluid above the leakless stop valves 806 and 806A, to effectively keep the rolling mill spring constant at a high value. During rolling, the control system 801 that may be of the type as shown in FIG. 11 is used to monitor and control the flow from an oil pan not shown to and from the sides of the pistons 804, 804A that are opposite from the sides that are connected to the valves 805, 805A;by opening the leakless stop valves 806 and 806A little-bylittle with the valves 805 and 805A being open, the lower inner roll group and housingpart 6 will move downwardly as the hydraulic fluid from the cylinders 90, A inoves the pistons 804 and 804A to the right exhausting hydraulic fluid through the valve 809. With such downward movement of the lower inner housing part, the rolls 1 or the intermediate rolls 2 and 3 may be changed. After changing the rolls or the like, the electromagnetic valve 809 is so changed again that the oil flows from the oil pan under pressure through the valve 809 to the right hand sides of the pistons 804 and 804A to correspondingly move the pistons 804 and 804A to the left to a predetermined position, after which the leakless stop valves 806 and 806A are closed along with closing of the valve 809 to again isolate the hydraulic fluid above the leakless stop valves 806 and 806A. Thus, the roll changing is accomplished easily and without changing the initial uniform roll gap with respect to the roll axial direction, becausewith movement of the inner housing part 6' either upwardly or downwardly, the hydraulic fluid in the circuit for the jack cylinder 90 changed in exactly the same manner and amount as the quantity of the hydraulic fluid in the jack cylinder 90A changed due to the isolation provided by. the leakless stop valves 811 and the synchronizing cylinder 802, 802A with their coupling 803.

Since the operation of the controls and rolling mill have been set forth along with their structure, the operation will not be reviewed separately.

While a preferred embodiment of the present invention has been set forth in considerable detail for purposes of illustration, with the details being important, further variations, embodiments and modifications are contemplated within the broader aspects of the present invention as determined by the spiritand scope of the following claims.

What is claimed is:

l. A multistage rolling mill having a roll arrangement of the Sendzimir cluster roll system in which each of an upper and lower half roll grouping has two drive rolls, respectively, the improvement comprising: an upper inner housing carrying therein said upper-half roll group; a separate lower inner housing carrying therein said lower-half roll group; a separate integral one piece outer housing encompassing and mounting therein said upper and lower inner housings; pass line adjusting means between one of said inner housings and said integral outer housings for providing adjusting vertical bodily linear movement between said one inner housing and said outer housing; and a rolling reduction adjusting means between the other inner housing and said integral outer housing for providing adjusting vertical bodily linear movement between said other inner housing and said outer housing separately from said pass line adjusting means.

2. A multistage rolling mill as defined in claim 1, wherein said integral outer housing is provided with stationary keeper plate guide means for guiding each of the upper and lower housings for vertical movements.

3. A multistage rolling mill as defined in claim 2, further including hinged doors on each axial side of the rolling mill providing thrust bearings for the rolls of said upper and lower roller groups.

4. A multistage rolling mill as defined in claim 1, including hinged central doors on each axial side of the roll groups, with each door having thrust bearing means engaging the adjacent axial end of the work rolls for restricting axial movement and absorbing the axial forces of rolling.

5. A multistage rolling mill as defined in claim 1, wherein each of said upper and lower half roll groupings has a plurality of back-up rolls with eccentric mountings for adjusting them toward and away from their respective inner housing to constitute crown adjusting means.

6. A multistage rolling mill as defined in claim 1, including a central door hingedly mounted on each axial end of said outer integral housing for swinging movement toward and away from said roll groupings; each central door including a roller mounted thereon for rotation about an axis perpendicular to the axes of the rolls in said roll groupings and having a peripheral face engaging the axial end face of each working roll of the roll groups; and separable fixing means on the opposite side of said door roller from its hinged mounting for securing said opposite side to said integral outer housing.

7. A multistage rolling mill as defined in claim 6, wherein said latch means includes a wedge surface rigidly mounted on said integral housing, and a cooperating wedge surface movably mounted on said end of said door.

8. A multistage rolling mill as defined in claim 6 wherein said separable fixing means is a latch means.

9. A multistage rolling mill as defined in claim 1, wherein each of said upper-half roll group and said lower-half roll group consists essentially of a work roll, two first intermediate rolls in engagement with said work roll, three second intermediate rolls in engagement with said first intermediate rolls, and four eccentrically adjustable back-up rolls in engagement with said second intermediate rolls; and further including means for driving two of said intermediate rolls to constitute said two drive rolls for each of said half roll groups.

10. A multistage rolling mill having a roll arrangement of the Sendzimir system in which each of an upper and lower half roll grouping has two drive rolls, respectively, the improvement comprising: an upper inner housing carrying therein :said upper-half roll group; a separate lower inner housing carrying therein said lower-half roll group; a separate integral outer housing encompassing and mounting therein said upper and lower inner housings; a central door hingedly mounted on each axial end of said. outer integral housing for swinging movement toward and away from said roll groupings; each central door including a roller mounted thereon for rotation about an axis perpendicular to the axes of the rolls in said roll groupings and having a peripheral face engaging the axial end face of each working roll of the roll groups; and separable fixing means on the opposite side of said door roller from its hinged mounting for securing said opposite side to said integral outer housing. 

1. A multistage rolling mill having a roll arrangement of the Sendzimir cluster roll system in which each of an upper and lower half roll grouping has two drive rolls, respectively, the improvement comprising: an upper inner housing carrying therein said upper-half roll group; a separate lower inner housing carrying therein said lower-half roll group; a separate integral one piece outer housing encompassing and mounting therein said upper and lower inner housings; pass line adjusting means between one of said inner housings and said integral outer housings for providing adjusting vertical bodily linear movement between said one inner housing and said outer housing; and a rolling reduction adjusting means between the other inner housing and said integral outer housing for providing adjusting vertical bodily linear movement between said other inner housing and said outer housing separately from said pass line adjusting means.
 2. A multistage rolling mill as defined in claim 1, wherein said integral outer housing is provided with stationary keeper plate guide means for guiding each of the upper and lower housings for vertical movements.
 3. A multistage rolling mill as defined in claim 2, further including hinged doors on each axial side of the rolling mill providing thrust bearings for the rolls of said upper and lower roller groups.
 4. A multistage rolling mill as defined in claim 1, including hinged central doors on each axial side of the roll groups, with each door having thrust bearing means engaging the adjacent axial end of the work rolls for restricting axial movement and absorbing the axial forces of rolling.
 5. A multistage rolling mill as defined in claim 1, wherein each of said upper and lower half roll groupings has a plurality of back-up rolls with eccentric mountings for adjusting them toward and away from their respective inner housing to constitute crown adjusting means.
 6. A multistage rolling mill as defined in claim 1, including a central door hingedly mounted on each axial end of said outer integral housing for swinging movement toward and away from said roll groupings; each central door including a roller mounted thereon for rotation about an axis perpendicular to the axes of the rolls in said roll groupings and having a peripheral face engaging the axial end face of each working roll of the roll groups; and separable fixing means on the opposite side of said door roller from its hinged mounting for securing said opposite side to said integral outer housing.
 7. A multistage rolling mill as defined in claim 6, wherein said latch means includes a wedge surface rigidly mounted on said integral housing, and a cooperating wedge surface movably mounted on said end of said door.
 8. A multistage rolling mill as defined in claim 6 wherein said separable fixing means is a latch means.
 9. A multistage rolling mill as defined in claim 1, wherein each of said upper-half roll group and said lower-half roll group consists essentially of a work roll, two first intermediate rolls in engagement with said work roll, three second intermediate rolls in engagement with said first intermediate rolls, and four eccentrically adjustable back-up rolls in engagement with said second intermediate rolls; and further including means for driving two of said intermediate rolls to constitute said two drive rolls for each of said half roll groups.
 10. A multistage rolling mill having a roll arrangement of the Sendzimir system in which each of an upper and lower half roll grouping has two drive rolls, respectively, the improvement comprising: an upper inner housing carrying therein said upper-half roll group; a separate lower inner housing carrying therein said lower-half roll group; a separate integral outer housing encompassing and mounting therein said upper and lower inner housings; a central door hingedly mounted on each axial end of said outer integral housing for swinging movement toward and away from said roll groupings; each central door including a roller mounted thereon for rotation about an axis perpendicular to the axes of the rolls in said roll groupings and having a peripheral face engaging the axial end face of each working roll of the roll groups; and separable fixing means on the opposite side of said door roller from its hinged mounting for securing said opposite side to said integral outer housing. 